Commit 4672694b authored Jul 30, 2018 by Eric Dumazet Committed by David S. Miller Jul 31, 2018

ipv4: frags: handle possible skb truesize change



ip_frag_queue() might call pskb_pull() on one skb that
is already in the fragment queue.

We need to take care of possible truesize change, or we
might have an imbalance of the netns frags memory usage.

IPv6 is immune to this bug, because RFC5722, Section 4,
amended by Errata ID 3089 states :

  When reassembling an IPv6 datagram, if
  one or more its constituent fragments is determined to be an
  overlapping fragment, the entire datagram (and any constituent
  fragments) MUST be silently discarded.

Fixes: 158f323b ("net: adjust skb->truesize in pskb_expand_head()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 56e2c94f

net/ipv4/ip_fragment.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -383,11 +383,16 @@ found:
		int i = end - next->ip_defrag_offset; /* overlap is 'i' bytes */

		if (i < next->len) {
		int delta = -next->truesize;

		/* Eat head of the next overlapped fragment
		* and leave the loop. The next ones cannot overlap.
		*/
		if (!pskb_pull(next, i))
		goto err;
		delta += next->truesize;
		if (delta)
		add_frag_mem_limit(qp->q.net, delta);
		next->ip_defrag_offset += i;
		qp->q.meat -= i;
		if (next->ip_summed != CHECKSUM_UNNECESSARY)

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